(the type of milk produced at the end stages of pregnancy), providing much needed immune support to newly born infants. It was widely believed that lactoferrin was only a bacteriostatic agent due to its high iron affinity and its ability to sequester free iron atoms from pathogenic microbes. It is now known, however, that the major antimicrobial driving force lies in the bactericidal properties of its iron-bound pocket and a specific peptide lactoferricin located at the N-lobe. Lactoferrin is able to bind to the LPS (lipopolysaccharide) layer of bacteria, and in its holo form the iron atom oxidizes the lipopolysaccharides to lyse the outer membrane and simultaneously produce toxic hydrogen peroxide. Additionally, upon cleavage of lactoferrin by trypsin, the peptide lactoferricin is produced which binds to H+-ATPase, disrupting proton translocation and ultimately killing the cell. Ferritin Ferritin is an iron reservoir for an individual cell. It is found in all cells types and localized in the cytosol. Ferritin is a large protein composed of 24 subunits surrounding a core full of iron atoms. It is capable of holding 0-4500 iron atoms, which can be used as a reservoir for cellular needs. Iron is stored when there is excess, and retrieved when iron is needed again. The subunits are a mixture of H (heavy or heart) and L (light or liver). The subunits form a cluster 70-80 Angstroms wide, which is then filled with iron ferrihydrite. Ferritin is a highly conserved protein through all domains of life. It is so conserved that subunits from horses and humans can assemble together into a functional protein. Each subunit is composed of five alpha helices. Ferritin is used to diagnose low iron levels in humans. It can be used to indicate the level of bioavailable iron, which is helpful for diagnosing anemia. The usual range for men is 18-270 ng/mL and the range for women is 18-160 ng/mL. See also Iron External links References Iron metabolism